Flexible packaging has long been used to package products such as books, compact discs, cassette tapes, and a host of other types of items to provide protection when shipping or mailing the items, and in some cases to hermetically seal the objects from the outside environment. Web-handling machines have been developed to automate the process of packaging objects in flexible packaging materials. Dual-web machines bring a pair of webs into generally parallel confronting relation with each other and feed a product, or a group of products, between the webs. Longitudinal or side seals are then effected to seal the webs together along their side edges, and transverse or cross seals are similarly made ahead of and behind the packaged product(s), thus forming a package containing the product(s). The package is severed from the remainder of the webs to complete the process. Single-web machines work similarly, except a single web is either supplied to the machine as a C-fold, or a flat web is manipulated and folded into a C-fold configuration, the objects to be packaged are inserted between the two opposing portions of the C-folded web, and one longitudinal seal and two cross seals are formed.
Single-web machines typically include a longitudinal seal device such as a pair of rolls or the like forming a nip through which the overlying longitudinal edges of the opposing web portions pass to effect a longitudinal seal on one side of the package. Dual-web machines include a similar longitudinal seal device through which the opposite longitudinal edges of the web portions pass to effect an opposite longitudinal seal. The longitudinal seal devices can apply pressure alone where cold seal materials are employed, or can apply pressure and heat in the case of heat-seal materials. The longitudinal seal devices are spaced apart by a distance corresponding to the width of the web material. Typically this distance is fixed, such that the machine is able to handle only one width of material.
Generally there is an open space between the two longitudinal seal devices, and the object to be packaged passes through this space. One problem with such machines is that if the object to be packaged is considerably narrower than the space between the longitudinal seal devices, the object may be able to shift around within the resulting package. This is undesirable in many cases; for example, the object may be able to shift into a position close to one corner of the package and thus be more susceptible to being damaged if the package is dropped on the corner. Thus, such machines have disadvantages when it comes to packaging a variety of objects of different sizes and/or different shapes.
With conventional machines, another problem that frequently arises is that the packaged object is not centered between the two web portions in the thickness direction of the object, i.e., in a direction normal to the surfaces of the web portions. If the object is offset in the thickness direction toward one web portion, the frequent result is that the overlying longitudinal edges of the web portions are not properly aligned with each other; the edge (or both edges in the case of a dual-web machine) of the web portion toward which the object is offset tends to be pulled transversely inward toward the longitudinal centerline of the web portion because the web portion must curve outward to a greater extent than the other web portion. This results in package edges that are unsightly.
Another problem with many types of flexible packaging machines of the above-noted type is that the web materials tend to become wrinkled as a result of being forced to bend and curve by the contour of the object being packaged. In some cases, no attempt is made to eliminate the wrinkling, and the result is that packages are made that are not very aesthetically pleasing. The problem tends to become worse as the height or thickness of the packaged object increases, since the web material is forced to curve and bend to a greater extent. Furthermore, different types of web materials behave differently with respect to wrinkling. Therefore, the conventional machines are not well suited to packaging a variety of objects of different thicknesses, sizes, and shapes, since a machine set-up that may minimize wrinkling for one object configuration and/or one type of web material may not work well for a different object configuration and/or different web material.
Some machines are designed to be adjustable for different web widths in an attempt to address some of the above problems. For instance, the two spaced longitudinal seal devices in some machines are adjustable in position so they can be moved closer together when running a narrower web material for smaller objects, or farther apart when running a wider web material for larger objects. This approach, however, is unappealing because it complicates the design of the machine, and changing the machine set-up wastes time that could better be used producing packages. Furthermore, if the range and number of object configurations are substantial, it might be necessary to switch between several different widths of the same web material, which would be cumbersome, particularly if object configurations were changed frequently.
In light of the above considerations, a more versatile packaging machine and method are needed, able to handle various object configurations with a lessened need for hardware adjustments. Also needed is a packaging machine and method for producing packages with reduced wrinkling of the flexible packaging materials even when a change is made in the object configuration and/or type of packaging material. Moreover, there is a need for a packaging machine and method for producing packages that reduce shifting around of the packaged object and that provide improved corner protection; ideally, the machine and method would substantially center the packaged object in the thickness direction so that the overlying longitudinal edges of the web portions line up with each other.